Plant for continuous mixing and homogenization

ABSTRACT

The new invention is directed to a continuous mixing and homogenizing plant, particularly for mill products. In so doing, the simultaneity of the mixing of all raw components in a pre-mixing space 8 is ensured in particular, so that subsequent continuous homogenization is also possible so as to meet the strictest demands. The utilized component weigher 4 and the assigned screw discharge 25 are constructed so as to be substantially tubular and together form a differential flow regulator 6. The inner surface of the entire system contacted by the product is accordingly tubular and is subjected to a continuous self-cleaning as a result of the movement of the product. Further, it is possible to arrange a plurality of component weighers 4 in a geometrically identical manner with respect to a collecting point 17 and a very high quality of mixing is obtained.

This application is a division, of application Ser. No. 08/375,169,filed Jan. 18, 1995, now U.S. Pat. No. 5,527,107, which is continuationof application Ser. No. 08/156,410, filed Nov. 19, 1993, now abandoned,which is a continuation of application Ser. No. 07/768,640, filed Dec.2, 1991, now abandoned.

TECHNICAL FIELD

The invention is directed to a plant for mixing and homogenizingpourable materials to be ground comprising a plurality of continuouslyoperating component metering weighers.

BACKGROUND ART

Formerly, in order to mix and homogenize pourable materials to beground, particularly raw components for the foodstuff and feedstuffindustries. The so-called batch mixer was used almost exclusively. Thesebatch mixers enable a thorough mixing and a high degree of homogeneitywith respect to all raw components, even the smallest, e.g. for theproduction of a baking mixture. In practice, there are a great number ofconcepts having particular characteristics depending on the technicalfield. In the simplest solution, the batch mixer is constructedsimultaneously as a hopper scale. The required raw components areweighed in one after the other, according to a predetermined recipe, bymeans of the weight signals and are subsequently homogenized with themixing tools comprehending the entire batch container. The homogeneitycan be controlled advantageously in this instance by means of a suitableconstruction of the mixing tools and optimal time period. However, thereare two fundamental disadvantages to this solution. Firstly, adiscontinuous operation results from the sharp separation of workcycles:

metering--weighing

mixing--homogenization

discharging

Secondly, the volume of the batch mixer, e.g. one to two cubic meters,and the time required for a mixing and homogenizing cycle determines thequantity which can be mixed per hour. Strict limits are accordinglyimposed on increases in output.

Attempts have been made to reduce these disadvantages in various ways,e.g. in that at least a portion of the raw components are addedsimultaneously by means of metering weighers. A genuine increase inoutput can accordingly be achieved by using a preliminary containerweigher in which a new mixture is prepared completely according to therecipe during the homogenization process and can be discharged into thebatch mixer within several seconds. Moreover, the time required fordischarging can be shortened when a secondary container of the sameproportions as the batch mixer is arranged subsequent to the latter, anentire batch being discharged into the secondary container in eachinstance. A continuous product flow can thus be delivered from thesecondary container via discharging elements. Thus, a high constructioncost is required for the continuous delivery of a homogenized productwith high hourly output, since a certain overall height or buildingheight is required in order to arrange the three containers one belowthe other so that the transfer of product can be effected by means ofgravity. If product mixtures which are processed one after the other maynot be contaminated or if very strict demands are made with respect tohygiene, a thorough cleaning must be performed periodically and certainresidues must be removed from the containers, if necessary, after everychange of mixture.

Recently, in order to reduce these disadvantages somewhat, continuoussystems have been used to an increasing extent. Solutions with beltweighers are known. So far, it has not been possible for this system toprevail in a broader market or to partially displace the batch mixer.Hygiene could be improved only in part. The homogeneity is not as goodas in the batch mixer in every case, but in particular the investmentcost for belt weighers is considerable in many cases. Simple meteringelements such as those used for liquids or for freely flowing grainproduct cannot be used because of the poor flowing properties of atleast a portion of the components or materials to be ground.

DISCLOSURE OF THE INVENTION

The object of the invention is to eliminate the known disadvantages,particularly to deliver the homogenized product in a continuous mannerand also to enable very high throughput capacities with a high degree ofhomogeneity with respect to all product components.

The solution, according to the invention, is characterized in that themixing and homogenizing plant comprises a pre-mixing space for thesimultaneous, continuous mixing together of the individual componentsfrom the component metering weighers.

Only the new invention shows with great clarity that the entire scope ofoperations, e.g. also the product path to the pre-mixing space, is ofgreat importance for the overall results when the strictest demands aremade with respect to adherence to the recipe with a plurality ofcomponents and with respect to the homogenization. In addition to theprecision of every individual device, not only must the technicalinteraction be kept under control, but the relative operation withrespect to time is also very important for a good end result. This facthas been overlooked in the past.

It is particularly preferable that at least a part of the componentmetering weighers be constructed as differential flow regulators,wherein the latter are constructed as tube weighers having a tubularcross section and a screw-type discharge for all product componentshaving poor flow properties, e.g. flour-like or flake-type productcomponents. However, for the mixing of flour and semolina, the freelyflowing semolina can be added in a metered manner by means of simplyconceived differential flow regulators comprising slides or flap controland the flour can be added in a metered manner by means of adifferential flow regulator comprising a screw-type discharge.

In a further development of the inventive idea, a plurality of componentmetering weighers can be arranged in a geometrically similar arrangementdirectly on a common collecting point or can be arranged in ageometrically similar manner relative to the pre-mixing space, so thatthe distances between the end of the discharge of all component meteringweighers and a common collecting point are approximately equal. Thissolution completely eliminates a former weak point in the continuoushomogenization of difficult materials to be ground. It has beenrecognized that a continuous mixing and homogenization requires that allindividual components be fed in simultaneously. The use of tube weigherswith tube screw conveyors as discharge means in the differential flowmeasuring principle in particular also allows a genuine simultaneousfeed of raw components which are difficult to meter, e.g. bran, break,or flour with a high fat content, so that no disturbances oruncontrollable mixing flows occur at the start, during operation or atthe end of a mixing task.

The weighing time can be reduced virtually to zero with the differentialflow measuring principle, since it is effected at the continuous productflow with very great precision and weighing accuracy. The unifying ofproduct flows is ideal and is effected in the same way as when coffee ispoured into a cup with one hand and milk is poured into a cupsimultaneously with the other hand in order to make a cup ofcafe-au-lait. The tubular cross section of a tube weigher, in the sameway as the tube screw conveyor, allows product to flow through theentire cross section in the particularly problematic interior of theweigher. As a result, the product actively brushes over substantiallyall inner surfaces during normal operation and a self-cleaning action isaccordingly effected. No product can adhere to or remain lying on anylocation. Virtually no residues, which pose a known problem in foodstuffprocessing, can occur. A total emptying of all elements can be providedin each instance after every change of product by means of correspondingprogramming of the entire control unit.

The component metering weighers preferably open horizontally into acollecting hopper or pre-mixing space, respectively, with a directtransfer of the material into a homogenizer, so that the quantitiesdischarged by the tube screw conveyors of the component meteringweighers converge directly in a common collecting point. The results canbe further improved if the construction design for the product transferfrom the tube screw conveyor to the collecting hopper is effected insuch a way that a stronger product flow does not displace weaker productflows to one side, when, rather, an immediate mixture is effected.

For many mixing tasks, additives must be mixed in very minimalproportions in addition to the mixing of two, three or more main rawcomponents. One or more micro-differential metering weighers can be usedfor this purpose. Further, it is preferable if a quantity of componentmetering weighers are arranged circularly and approximately at the sameheight relative to a collecting point, wherein the component meteringweighers are arranged in an outer circular ring and a plurality ofmicro-component weighers, if necessary, are arranged within the circularring. The great advantage of the new solution consists in that theindividual mixing proportions are formed immediately before combinationand are combined immediately before or shortly before thehomogenization. The requirement for the simultaneous combination of allmixing components can thus be ensured at the same time. A basicprecondition for the strictest requirements with respect to adherence tothe recipe, mixing, and homogenization is accordingly fulfilled.

A further, particularly advantageous construction is characterized inthat the pre-mixing space and homogenizer form a constructional unit,wherein the homogenizer operates in a continuous manner. Accordingly, itcould be shown once again that the long dispute between two technicalsolutions often only consists in an exaggerated stubbornness of bothrespective advocates and producers of two pure concepts and that byadopting only one formulation of the other solution unexpected advancescan be brought about. The mixing of a plurality of components impliesnothing more than simultaneity of the mixing, neither with respect to adetermined quantity, e.g. a sample quantity, nor with respect to amixing constant over a long period of time during continuous mixing. Forthis reason, the homogeneity or homogenizing is additionally prolongedin mixing performed in mills. Because of the many possible disturbingfactors, only the batch mixer system has so far been credited with aguarantee of complete homogeneity, in an identification, as it were,with the manner of thinking of a person accustomed to scientificlaboratory work. The small laboratory mixer was adopted on a large scaleat the price of a discontinuous, costly working process.

A controllable product return from the outlet of the homogenizer intothe pre-mixing space is preferably suggested, so that a recirculation ofthe product to be mixed from the pre-mixing space-homogenizer-pre-mixingspace, etc. is possible, e.g. when starting a mixing during disturbancesor at the end of a selectable quantity and/or over a selectable timeperiod. Since the product can only move forward in a classichomogenizer, there is only a transverse mixing (as seen in the directionof flow). However, a longitudinal mixing can now be compelled in a novelmanner.

It is particularly advantageous if the pre-mixing space and homogenizerform a constructional unit and if the latter is conceived as acontinuously working pneumatic homogenizer which can comprise a centraloutlet tube. An adjustable base outlet is preferably formed in the basearea of the central outlet tube, so that this adjustable base outlet iscontrollable via computing means and/or qualitative sensor means on thebasis of qualitative values such as moisture, brightness, protein, crudefiber, etc. In a further development of the inventive idea, thehomogenizer can also be constructed as a mechanical vertical conveyorwith homogenizing elements, that is, with a lifting function and with acontrollable return movement into the pre-mixing space. The verticalconveyor is preferably arranged above a controllable base outlet of thepre-mixing space.

With very strict demands on the homogeneity of the final product,pneumatically operating means or mechanical mixing tools can be arrangedin the pre-mixing space. In so doing, controllable product dischargemeans are to be assigned to the vertical conveyor for controlling theproduct discharge and product return. In any case, it is suggested forautomatically operating plants to arrange a measuring and monitoringdevice at the outlet of the homogenizer for qualitative productparameters. For special applications, e.g. for feedstuff mixtures, aproduct mixing and holding station can be arranged for the productsubsequent to the homogenizer, a product circulating conveyor preferablybeing assigned to the latter.

Most products which are sometimes considered difficult can besuccessfully processed and mixed with the new invention. Depending onthe application, this is a matter of different qualities of flours,semolina, middlings, bran, etc. and ingredients such as dry gluten,coloring, vitamin C, calcium, phosphate, powdered egg, salt, bakingpowder, etc. or corresponding feed components for feedstuff. However,instantaneous weight signals for the metering of water or other liquidcomponents can also be made used of.

Further, the new invention makes it possible simultaneously to controldirectly the metered addition of water and egg soup or, e.g. liquids,for special mixing tasks, e.g. mixing for pasta or brothproduction--since instantaneous values of throughput per hour unit canbe determined at all times with very great precision.

DESCRIPTION OF THE INVENTION

The invention is now explained in more detail with reference to someembodiment examples:

FIG. 1 shows a schematic overview of the new continuous mixing andhomogenizing plant;

FIG. 2 shows a pre-mixing space;

FIG. 3 shows an outline for the circular arrangement of componentmetering weighers relative to the pre-mixing space;

FIG. 4 shows an embodiment form with the additional use of a productstation;

FIG. 5 shows a mechanical pre-mixer homogenizer;

FIG. 6 shows a simplified pre-mixer homogenizer;

FIG. 6a shows the same arrangement as in FIG. 6, but for the strictestdemands with respect to homogeneity;

FIG. 7 shows a pneumatic homogenizer.

METHODS FOR CARRYING OUT THE INVENTION

FIGS. 1, 2 and 3 are referred to in the following. A raw material A isfed from a component cell 1 via a discharge apparatus 2 and a screwconveyor or pocket wheel 3 into a component metering weigher 4. Thecomponent metering weigher 4, together with a tube screw conveyor 5,forms a differential flow regulator 6. A raw material B is dischargedfrom a second component cell 1', a discharge apparatus 2' and a conveyorscrew 3' and given in a metered manner to a second component meteringweigher 4 or a corresponding differential flow regulator 6. The weightamounts which are predetermined by a control unit 7 are directedsimultaneously by the two differential flow regulators 6 into apre-mixing space 8 and directly into a homogenizer 9 and conveyed forfurther processing (arrow 11) via an outlet spout 10. As can be seen inFIGS. 1, 2 and 3, the outlets 26, 26' etc. of the component meteringweighers 4 are arranged at identical distances from a collecting point17. The entire product flow is controlled by the control unit 7. Thecorresponding signals are transmitted to all corresponding plantelements by the control unit 7 or mixer computer 7, respectively. Inparticular, each of the component metering weighers 4 receives an exactmetering command via a control line 12. On-site electronics 13 transmitsthe required signals, e.g. to the feed apparatus 2/3 or 2'/3',respectively, and correspondingly switches a vibrator 14/14' on or off,respectively. Another signal is likewise fed to a drive unit 15 of thetube screw conveyor 5 in order to predetermine a volumetric referencemetering output for the start by means of the rate of rotation, whichreference metering output is then replaced at the end of the volumetricmetering by a weight value per time unit by means of the differentialweighing and is regulated correspondingly according to a predeterminedmixing composition or recipe.

In many cases of application, one or more additives are added to themixture of two or more basic components, e.g. two types of flour, but invery small proportions. Special micro-differential metering weighers 16,known per se, are used for this purpose. If only one micro-differentialmetering weigher 16 is required, it can be arranged directly above thepre-mixing space 8. All described raw components are accordingly guidedtogether to an (imaginary) collecting point 17 and flow directly intothe homogenizer 9. The homogenizer 9 comprises a drive 18 which drives apaddle shaft 19 at relatively high circumferential speed in such a waythat an intensive whirling occurs from a great number of paddles 20inside a closed tubular housing 21.

As can further be seen in FIG. 1, the differential flow regulator 6 isconnected, as a constructional unit, with a stationary product feed 30via a flexible sleeve 31 and is likewise connected at the outlet end ofthe tube screw conveyor 5 with the stationary collecting hopper 8 via arubber sleeve 32. The required measuring elements, known per se, for theweight values or weight value receivers are not shown.

In principle, the component metering weigher 4 cooperates with the feedelement 3 and the tube screw conveyor 5 as well as with thecorresponding control means as differential flow regulator 6. If aproduct quantity has reached a selectable filling height in thecomponent metering weigher 4, the feed of additional product via thefeed element 3 is stopped via a corresponding weigher signal. The actualweight per product quantity in the weighing vessel 24 can be determinedat least when starting the plant after a short calming period in theweigher and the product discharge can commence by means of switching onthe drive unit 15. If corresponding numerical values are stored in thecontrol unit 7 the desired output can be discharged by means of settinga determined speed of the tube screw conveyor 5. The metering outputdetermined by this is a function of the speed and volumetric efficiencyof the tube screw conveyor 5. This means that the metering accuracybrought about by the volumetric metering is not as good as that of thedifferential weight measurement. A reduction in weight is determined inthe component metering weigher 4 already with small dischargequantities. The weight reduction per time unit allows a changeover intothe gravimetric determination of the discharged material. The change inspeed of the tube screw conveyor 5, which is necessary in any case, canbe corrected via the drive unit 15 almost without a delay in time withthe more precise gravimetric measurement value. In principle, theconveying path between the outlet 26 (FIG. 3) of the tube screw conveyor5 or a corresponding second outlet 26' of every additional componentmetering weigher 4, respectively, until the convergence of theindividual partial flows is identical. After a certain metering timeinterval, the contents in the weighing vessel 24 have sunk to a lowerfilling level. At this value, which is assumed as lower fillingquantity, a signal is given once again for actuating the feed element 3and the weighing vessel 24 is refilled. During the filling, the weightsignal may not be used for the metering output of the tube screwconveyor 5. However, a corresponding stored or predetermined value or aspeed assigned to the metering output, respectively, can be maintainedor the last measured speed of the discharge screw conveyor can be keptconstant during the filling period. The plant is particularly suitedpreferably for the mixing of flour-like materials, particularly inmills, feedstuff mills, bakeries or e.g. also the preparation ofmaterials in pasta factories, at least the components which arefree-flowing to some degree. But additional liquid components can alsobe mixed in in the area of the homogenizer 9 with an appropriateconstruction design.

FIG. 4 shows a similar construction in a more schematic manner than inFIG. 1. The product is fed into a pre-mixing space 8 and from the latterdirectly into a continuous homogenizer 9 via the force of gravity. Thissolution is for simple mixing tasks. The homogenizer 9 is shown in acorrespondingly simplified manner. An NIR measuring and monitoringdevice 47 is arranged at the product outlet of the homogenizer 9, theproduct is then fed to a product discharge line 41 via a horizontalscrew 40. In this construction, the first runnings which areinsufficiently homogenized can be delivered, via a second vertical screw42, to a product station 43 from which they are directed in turn, via ametering lock 45 and a diverter or line-switch 44, to the productdischarge line 41 in the smallest quantities via an inlet tube 46.However, it is also possible to homogenize the product in the productstation itself by means of repeated circular conveying in that it isreturned to the horizontal screw 40 and vertical screw 42 from theline-switch 44. As in FIG. 1, all monitoring, control and regulatingtasks can likewise be effected in this case via a PC or mixer, computer7.

The quality of mixing in the continuous method also depends on thehomogeneity of the individual raw components. For this reason, FIG. 4shows a possibility for the homogenization of different raw components.A plurality of raw components of the same kind are combined in groupsand fed to a differential throughflow regulator in respectiveproportions e.g. of 25%, 33% and 50%. However, every proportion needonly be fed within an accuracy of +/-5% in each instance. This meansthat inexpensive discharge elements, e.g. rotary locks, withpreselectable discharge speeds can be used among the corresponding silocells 1', 1", 1'" with raw components of the same kind. However, theblend of the group is in turn determined with weighing accuracy viacomponent metering weigher 16' and controlled in the correspondingdirection to the other component metering weighers 16.

FIG. 5 shows a particularly advantageous construction, wherein thepre-mixing space 8 is designed as a combinatorial unit with thehomogenizer 9. Additional simple mixing tools 50 which can have a formwhich is known per se are arranged in the pre-mixing space 8 in FIG. 5.It is important that, in this case also, all product proportions enterthe pre-mixing space 8 simultaneously and with weighing accuracy incorrect combination, so that a good mixing takes place. The actualhomogenization, that is, the uniform fine distribution of all componentsis effected in the mechanical whirl homogenizer 51. In the hopperportion 52, a feed screw 53 conveys the entering product into the whirlhomogenizer 51 which is outfitted with homogenizing paddles 54. Thiswhirl homogenizer 51 is set in rotation by a drive motor 55 whoserotating direction can be reversed. In so doing, the mixing tools 50 canbe set in rotation by the same drive. The product is first directed froman overflow 56 via a NIR measuring and monitoring device 47, from whereit either flows back into the pre-mixing space 8 via a return line 57 oris fed via a discharge lock 58 to a further destination. In very simplecases, e.g. for mixing together two flours, the material to be mixed isdischarged directly from the pre-mixing space 8 via a controllable baseflap 59 and transferred via a conveyor 60 to the same destination as itis from the discharge lock 58. In the converse case, first runningsand/or residual quantities can likewise be transferred for residuesprocessing 62 via the base flaps 59 and line-switch 61 with particularlystrict demands on homogeneity.

Reference is made in the following to FIG. 6 which shows, in part, asimplified embodiment form of FIG. 5. In particular, the collectinghopper 8 is formed by a simple combined pre-mixing space and homogenizerin which corresponding homogenizing tools, which can also besupplemented by liquid means (e.g. as in FIG. 7), are arranged. Thistype of construction can always be used when e.g. only different floursneed to be mixed and homogenized, that is, when no minimal componentsneed be added.

Another particularly advantageous construction is shown in FIG. 6 inthat it is possible for the first time to guide the main productcontinuously produced by the mill, e.g. baking flour or pasta semolina,directly via a first master weigher 63. The master weigher 63 measuresthe continuous product flow M of the mill and directs it directly intothe pre-mixing space 8. A small pre-station 64 prior to the differentialweigher takes over the build-up of material in the gravimetric measuringphase. All the rest of the components can now be delivered andhomogenized in the desired proportion percents based on a predeterminedrecipe and the instantaneous weight signals of the master weigher 63with a dependent metering weigher 65, 66, 67 etc. via a correspondingcontrol unit similar to FIGS. 4 and 5, but so as to be continuouslycorrected with respect to weight.

But it is accordingly possible for the first time also to producehomogeneous flour mixtures in continuous operation according to theworking process in the mill, which is continuous per se, withoutcorresponding intermediate storage, which constitutes a great advancewith all products which do not need storage with respect to productquality.

FIG. 6a shows another construction of FIG. 6. All advantages, e.g. ofFIG. 5 as well as FIG. 6, that is, for the strictest demands withrespect to the homogeneity, even with the minimal components, can befulfilled. A geometrically similar arrangement of all differentialmetering devices relative to the pre-mixing space 8 is symbolized by 8',e.g. corresponding to FIGS. 1 to 3.

FIG. 7 is an alternative to FIGS. 5 and 6. The pre-mixing space 8 andhomogenizer 9 are combined to form a pneumatic homogenizer 70 in thisinstance. The product feed can be effected in the same manner as in FIG.5. In normal operation, all product proportions are fed into thepre-mixing space 8 until reaching the level of the overflow 72 of amixing tube 71. At the same time, air is blown in via a double-base 73with porous plate by a blower 74 by means of an adjustable air throttle75. An outstanding homogeneity, particularly for mill products, can beachieved with dry air in that the individual components are fed in moreat the periphery, but the material to be mixed, which is homogenized bymeans of liquefaction and intensive whirling, flows toward the center(arrow 76) and the air is likewise sucked out in the center via an airexhaust 77. The outlet area of the pneumatic homogenizer 70 isconstructed in such a way that e.g. the proportion at the base outlet 78is controllable by means of raising and lowering the mixing tube 71,which is also particularly useful for emptying residue.

The invention further allows a great number of other novel combinationpossibilities, only some of which are shown in the drawings. Allconstructions of FIGS. 4 to 7 which are shown schematically arepreferably constructed in a manner corresponding to FIGS. 1, 2 and 3with respect to the arrangement.

We claim:
 1. An aparatus for transporting foodstuff materialcomprising:a foodstuff material product discharge line; a conveyor forreceiving and transporting the mixed foodstuff material to the productdischarge line; a product station for temporarily storing the foodstuffmaterial being operatively connected to the conveyor and the productdischarge line; and a controller operatively connected to said productstation, the product discharge line, and the conveyor, wherein theconveyor further comprises a horizontal screw for receiving the mixedfoodstuff material, the discharge line being connected to the horizontalconveyor, and a vertical screw operatively connected to transport thefoodstuff material from the horizontal conveyor to an inlet in theproduct station.
 2. The apparatus according to claim 1 furthercomprising a device operatively connected to the controller formonitoring and measuring the foodstuff materials being received by theconveyor.
 3. An apparatus for transporting foodstuff materialcomprisinga foodstuff material product discharge line; a conveyor forreceiving and transporting the mixed foodstuff material to the productdischarge line; a product station for temporarily storing the foodstuffmaterial being operatively connected to the conveyor and the productdischarge line; a controller operatively connected to said productdischarge line,and the conveyor; and a metering lock and a diverteroperatively connected to an outlet of the product station for divertingthe foodstuff materials to one of the product discharge line and theconveyor, said metering lock also be operatively connected to saidcontroller.